1. Field of the Invention
This invention relates generally to the art of connecting data terminal equipment (DTE) users to remote computer systems (or hosts) through a wireless or radio wave data communication network. The invention disclosed may, however, be useful for other forms of data transmission and communication systems.
2. Description of the Related Art
Over the past several decades, various communication networks have evolved to meet the growing need for access to information. Among the more familiar types of systems used for communication are wire-based telephone communication systems that use physical wires or optical fiber links to connect users. Data transmission using wire-based telephone communication systems can be accomplished using existing AT Modem technology. An AT Modem is a standard data communication equipment (DCE) connection device used with telephone equipment for converting or modulating an asynchronous stream of data into a phone line carrier signal. The connection between an AT Modem and a DTE, such as a personal computer or a portable computer, is usually through an RS-232 interface. One of the principal disadvantages of a wire-based telephone communication network is that users are limited to specific locations where wired connections are available. Another disadvantage is that wire-based telephone communication networks usually require dedicated telephone lines, which can be expensive.
Recently wireless data communication networks have emerged that enabled information exchange by sending and receiving data through high frequency radio signals. Examples of such networks include the Mobitex Radio Network (Mobitex), which is operated by RAM Mobile Data, and Ardis, which is a joint venture of Motorola and IBM. Mobitex was developed in Sweden by Ericsson/Eritel and has been installed and is maintained in many other countries. For example, in Canada, Mobitex is operated by Roger's Cantel. Making efficient use of these wireless data communication networks to connect DTE users to remote computer systems is one of the objects of the present invention. The Mobilex network will be used throughout the present application for illustrative purposes, but those skilled in the art will appreciate that other networks or applications may be used in connection with the present invention.
Electronic data communication is organized into networks that have established protocols and specifications. Communication between computers takes place over a connection that is established using a common protocol. A data communication network generally refers to a collection or grouping of computers organized for co-operative communication of data. Once a connection is established, there are a number of data transfer methods used by various data communication networks. Both Mobitex and Ardis use packet switched data transfer methods, which aggregate data into blocks called packets before it is transmitted.
Ericsson also manufactures a device called a Mobidem, which is a radio based modem that is capable of transmitting digital information across the Mobitex data communication network. The present invention adds software to a device such as a Mobidem so that it can communicate with the DTE User using an industry standard AT Command interface, called the Mobidem-AT. Communication between Mobitex and existing data communication networks or just single personal computers is now possible. Using a particular protocol, a gateway such as disclosed in the pending and commonly owned patent application Ser. No. 08/183,598 bridges the gap between the connecting parties in dissimilar networks. The objective of the gateway is to connect a Mobidem-AT to existing X.25-based network services to enhance the usefulness of Mobitex and the Mobidem-AT. The gateway product also provides enhanced speed, performance, and compatibility design when bridging different networks.
Many problems can arise when a wireless network, like Mobitex, attempts to supply connections to existing networks and computers such as an X.25 network. As the Mobidem-AT is used with a character-based DTE user the problems that must be solved include:
a) a padding method to be employed by the Mobidem-AT to ensure that every data packet has the maximum number of characters. By employing the disclosed padding method, the overall data throughput will be maximized and costs will be reduced. Most wireless networks charge their customers based on the number of characters in the packet, but charge less per character if there are more characters in the packet. Thus, having fewer characters per packet causes the price to transmit data to increase. PA1 b) access to a control channel to invoke remote gateway functions that can be performed on behalf of the DTE user and to send. Qualified (Q-Bit) information over X.25 to a remote computer system. Use of Qualified data in X.25 is clearly documented in the X.25 specification referenced in this document. PA1 c) increased security to allow private strings and passwords to be saved in the Mobidem-AT's stored dial strings. This allows the DTE user to use some advanced gateway functions and invoke them with fewer keystrokes thus increasing the speed of access and user friendliness. PA1 d) a method for scrolling the DTE user's screen to increase readability and ensure compatibility with a wider set of standard terminal packages available in the market today.
Solving these and other problems in a wireless data network is the purpose of the present invention.
Thus, providing an efficient padding method, access to the control channel, increased security methods, and an advanced scrolling method in the Mobidem-AT are critical for obtaining a fast, cost effective advantage for supporting communications for mobile users.